Full realization of the benefits of recent advances in molecular medicine requires the development of molecular imaging probes that target specific cells, receptors, aberrant genes, and proteins for therapeutic and diagnostic interventions. As with other imaging modalities, optical imaging using near-infrared (NIR) light (700-1700 nm) promises to become an important tool in healthcare. The NIR region of the spectrum, also known as the optical windows, offers important advantages for photon penetration deep into biological tissue. For fundamental studies of NIR photons with biological tissue and the development of molecular fluorescent probes optically active in NIR, we request to upgrade our 10 year old fluorometer to a state-of-the-art fluorescence spectrophotometer specifically dedicated to NIR. The requested system will be equipped with NIR light sources and ultrasensitive detectors, fluorescence lifetime, and polarization modules, will be highly flexible and will satisfy the urgent need of 13 NIH funded researchers from three major universities in the Saint Louis area: Washington University in St. Louis, University of Missouri -St. Louis, and Saint Louis University. The research that will be supported by this instrument includes diverse fields from the design of optically diverse contrast agents (organic dyes, polymer nanoparticles, gold nanocages, and fluorescent proteins), development of imaging modalities (fluorescence steady-state and lifetime imaging, photoacoustics, and optical tomography), to application of the probes and methods to tumor diagnostics, cancer treatment, bacteria detection, and understanding of brain function.